This section provides background information related to the present disclosure which is not necessarily prior art.
A lithium-ion battery includes a negative electrode, a positive electrode, and a separator there between. When the battery is charging, positively charged lithium ions move through an electrolyte from the positive electrode (cathode) to the negative electrode (anode), and in the opposite direction when the battery is discharging. The electrolyte can include a lithium salt, such as LIPF6, dissolved in an organic solvent, such as a mixture of linear and cyclic carbonate solvents.
Lithium-ion battery technology is used in many electrical devices including hybrid and electric vehicles. Batteries based on lithium-ion chemistry can be lighter than batteries based on nickel metal hydride and lead acid. Because an energy density of a lithium-ion battery can be higher than other battery types, lithium-ion batteries can boost both the range and power of hybrid and electric vehicles.
However, abusive electrical, thermal, or mechanical conditions can cause a lithium-ion battery to undergo self-heating and/or form ruptures in packaging, which can lead to incidents of undesirable performance. For example, abusive electrical conditions include overcharging the battery. Lithium-ion batteries can consequently cease functioning when subjected to high temperatures that may result from the abusive electrical conditions. These conditions can spread to adjacent cells.
Accordingly, the charge of a lithium ion battery can be monitored at any given time to ensure proper operation and use of the battery, for example, as the battery goes through various charging and discharging cycles. In this way, overcharging of the battery and high temperatures associated therewith can be mitigated. Monitoring can also help to manage and optimize the useful lifespan of the battery and can serve as an indicator for timely replacement of a battery that may be approaching the end of its service life.